He spent a year at Harrow School and subsequently matriculated at the University of Oxford. His father took delight in exhibiting the boy's musical and metrical gifts, and the precocious Theodore became a pet of the green room. At the age of 16, in conjunction with his father, he scored a dramatic success with The Soldier's Return, a comic opera, and it followed up with a series of popular ventures with John Liston and Charles Mathews, including Teleki.

He took up residence at St Mary Hall, Oxford University, leaving after two terms to resume his former life. His gift of improvising songs charmed the Prince Regent into a declaration that something must be done for Hook, who was appointed accountant-general and treasurer of Mauritius with a salary of £2,000 a year. He was the life and soul of the island from his arrival in October 1813, but a serious deficiency having been discovered in the treasury accounts in 1817, he was arrested and brought to England on a criminal charge. A sum of about £12,000 had been abstracted by a deputy official, and Hook was held responsible.

Hook, c. 1810

During the scrutiny of the audit board, he lived obscurely and maintained himself by writing for magazines and newspapers. In 1820, he launched the newspaper John Bull, the champion of high Toryism and the virulent detractor of Queen Caroline. Witty criticism and pitiless invective secured it a large circulation, and Hook derived, for the first year at least, an income of £2,000. He was, however, arrested for the second time on account of his debt to the state, which he made no effort to defray.

While he was confined in a sponging-house from 1823 to 1825, he wrote the nine volumes of stories afterwards collected under the title of Sayings and Doings (1824–1828). In the early 1820s, he helped the singer Michael Kelly compile his Reminiscences, which include details of working with Mozart. In the remaining 23 years of his life, he poured forth 38 volumes besides articles, squibs and sketches. His novels have frequent passages of racy narrative and vivid portraiture. They include Maxwell (1830), a portrait of his friend the Reverend E. Cannon; Love and Pride (1833); the autobiographic Gilbert Gurney (1835) and Gurney Married (1838); Jack Brag (1837) and Peregrine Bunce (1842). He did not finish a biographical work on Charles Mathews. His last novel was Births, Marriages and Deaths (1839).

The world's oldest postcard was sent to Hook in 1840.[1] Bearing a penny black stamp, Hook probably created and posted the card to himself as a practical joke on the postal service since the image is a caricature of workers in the post office.[1][2] In 2002, the postcard sold for a record £31,750.[1]

Work had already begun to tell on his health when Hook returned to his old habits and a prolonged attempt to combine industry and dissipation resulted in the confession that he was done up in purse, in mind and in body, too at last. He died at home in Fulham on 24 August 1841. His estate was seized by the Treasury. He never married but lived with Mary Anne Doughty; they had six children.